Characterizing Spatiotemporal Ground Deformation at Whakaari (White Island) Volcano, New Zealand From 2014 to 2024 Using InSAR Time-Series Analysis

Whakaari (White Island) volcano is the most active volcano in New Zealand with a dynamic hydrothermal system. The volcano has had four eruptive periods since 2014. In this study, our aim is to understand the pre-and post-eruption deformation processes occurring at Whakaari using interferometric synthetic aperture radar (InSAR). We analyze Copernicus Sentinel-1 Bursts from 2014 to 2024 from ascending and descending passes using small baseline subset (SBAS) InSAR time-series analysis. Four stacks are analyzed, one spanning approximately a decade from 2014 to 2024, and three short-term periods approximately 6 months before and after the 2016 and 2019 eruptions, and 6 months before the 2024 eruption. Together, these provide insights into the long-and short-term evolution of deformation at Whakaari. Results show spatially and temporally varied inflation-deflation cycles around the active crater lake area pre-and post eruptions. Long-term gradual uplift is observed east of the crater lake, whereas subsidence is observed south south-west of the crater lake. The nature of inflationary signatures vary prior to eruptions, which is interpreted as an effect of the pressure source (hydrothermal pressurization from a deep magma source, shallow magma, or crater lake-related processes). The nature of deflationary signatures is inferred to be related to post-eruption contraction of materials in the subsurface and movement and collapse of crater walls. The spatial and temporal variability in the observed deformation is correlated well with reported observations of gas emissions, eruptions, lava extrusion, and slope instabilities showing the usefulness of InSAR for volcano monitoring.